It is amply known to reinforce plastic products using fibers to meet particular mechanical or physical demands. Plastic products that are especially under stress can be provided with additional reinforcing structures. These reinforcements or functional components become increasingly important, given the continuous trend to provide plastic products of increasingly thinner wall thickness or system plastic products. This trend is based in particular on material-saving needs because material contributes substantially to the production price of a product as costs for raw material rise.
It was already known heretofore to provide certain products with ribs or similar external elements for mechanical reinforcement. It is further known to compression-mold or to shape soaked or impregnated plastic mats with a plastic material and then to subject it to back injection molding.
Furthermore, there is the trend for some time now to use injection molding or extrusion machines to incorporate fibers, especially glass fibers, into the plastic melt in order to enhance the mechanical properties of the entire product. The fiber orientation is oftentimes dependent on the flow behavior in such fiber-laden plastics so that the effective direction cannot be easily predefined. Moreover, the mostly short fiber elements are oftentimes amorphous and randomly arranged in their direction. Therefore, it is not possible to provide reinforcements in particular stress directions. Moreover, injection molding and extrusion applications permit heretofore only the production of limited fiber lengths because the fibers are broken, trimmed, or otherwise cut in the plasticizing device.
Plastic is increasingly used in many high-tech areas that encounter stress peaks only in certain regions or aligned high stress peaks. These products do not necessarily require the presence of reinforcements across the entire product; rather, these parts could be reinforced in some areas only so that the regions that are especially under stress are able to withstand the particular mechanical or physical demands. Still, the reinforcing measures should normally not be visible. Rather, it mostly desired to provide the respective products with same optic and haptic properties across the entire surface.